Re: [PATCH] build: do not require help2man at build-from-tarball time

[Jim Meyering]

Stefano Lattarini wrote:
...
> Just out of curiosity: is [test FILE -nt OTHER_FILE] a feature in POSIX?

Not in any current standard.

> Anyway, maybe it could be emulated with "find -newer" or something
> similar...

Sure, but not worth it, because some find programs probably lack support
for the -newer predicate.  Besides, I abandoned that approach because
it seemed like it would not be worthwhile, and because it would impose
overhead all of the time.

>> or when things are out of date, the regular commands
>> would run.  Otherwise, it would simply touch the .1 file and exit
>> successfully.
>>
>> AFAIK, there is no way in GNU make to specify dependencies that vary
>> depending on the existence of a target.  Does anyone know otherwise?
>> I.e., a rule that would apply when foo.1 does not exist, vs. another
>> one (with different dependents) that would apply when it does exist.
>>
> What about this (untested)?
>
>     ifeq ($(wildcard target)$(wildcard $(srcdir)/target),)
>     target: prereq1
>       @echo target existed already
>     else
>     target: prereq2
>       @echo target did not exist
>     endif
>
> That would only work assuming 'target' is relative to be builddir
> (i.e., 'dir/file', not $(srcdir)/dir/file'), but might be enough.

Nice.  That looks like it would work.
If only we could depend on GNU make...